Moisture sensing devices are utilized in number of sensing applications. One type of a conventional moisture sensing device is a humidity sensor, which can provide for the measurement of relative humidity (RH) over wide RH ranges (e.g., 1%-100%), but which continues to be a challenge in design and construction. Moisture sensing devices can be implemented in the context of semiconductor-based sensors utilized in many industrial applications. Solid-state semiconductor devices are found in most electronic components today. Semiconductor-based sensors, for example, are fabricated using semiconductor processes.
Many modern manufacturing processes, for example, generally require measurement of moisture contents corresponding to dew points between −40° C. and 180° C., or a relative humidity between 1% and 100%. Such devices do not, however, adequately measure the amount of moisture collected on a particular surface, which is an important factor in maintaining the efficiency and safety of manufacturing facilities. There is thus a need for a durable, compact, efficient moisture detector that can be used effectively in these processes to measure very small moisture content on surfaces.
Moisture can be measured by a number of techniques. In a semiconductor-based system, for example, moisture can be measured based upon the reversible water absorption characteristics of polymeric materials. The absorption of water into a sensor structure causes a number of physical changes in the active polymer. These physical changes can be transduced into electrical signals which are related to the water concentration in the polymer and which in turn are related to the relative humidity in the air surrounding the polymer. Such devices, however, are limited in range and efficiency and do not adequately detect moisture on surfaces.
Two of the most common physical changes are the change in resistance and the change in dielectric constant, which can be respectively translated into a resistance change and a capacitance change. It has been found, however, that elements utilized as resistive components suffer from the disadvantage that there is an inherent dissipation effect caused by the dissipation of heat due to the current flow in the elements necessary to make a resistance measurement. The result is erroneous readings, among other problems.
It is therefore believed that a solution to some of the problems associated with conventional moisture sensing devices involves the design and implementation of discrete components and circuits, based on simple principles of electrical conducting circuits, which to date have not been fully implemented in moisture sensing applications.